Muffler



Nov. 24, 1964 T. c. RICHMOND MUFFLER 2 Sheets-Sheet 1 Filed July 2, 1962 INVENTOR. 7/20/1105 C. Q/c/vmond A TTORNIS YS Nov. 24, 1964 'r. c. RICHMOND MUFFLER 2 Sheets-Sheet 2 Filed July 2, 1962 b INVENTORL. 77/0/7705 6? [Pk/1171000 BY 4. A4 ATTOR EYS 3,158,222 MUFFLER Thomas C. Richmond, Chestcrland, Ohio, assignor to Thompson Ramo Wooldridge Inc., Cleveland, Ohio, a corporation of Qhio Filed July 2, 1962, Ser. No. 206,819 Claims. (Cl. 181-59) The present invention relates to an improved exhaust mufiler for internal combustion engines.

A typical exhaust muffler is normally a modified form of an elementary low-pass acoustical filter including a through tube which is in fluid communication with closed cavities by virtue of small holes which appear at intervals along the tube. An eflicient mufiler must decrease the exhaust gas velocity and must also absorb the sound waves or cancel the sound waves by interference with other waves from the same source. Typically, a mufiier may include means for diverting the path of the exhaust gases into tortuous channels and re-combining the gas flow paths out of phase with each other before leaving the exhaust end of the muffler.

Typical mufiler constructions usually include a shell or other tubular housing containing a series of battles forming a number of resonating cavities, through which there extends a tubular multiple passage. The geometry of the openings and their number are designed to minimize the predominating frequencies in the exhaust to reduce the audible sound level to as low a value as possible. Any mufiler design, however, is necessarily a compromise because the predominating frequences in the exhaust gases vary with the engine speed and engine temperature.

Since there is no such thing as a universal mufiler, manufacturers of mufiiers are faced with the problem of carrying a very substantial inventory of mufil-er designs to accommodate different makes of cars and ditferent engines employed by the same manufacturers. The high cost of manufacture involved in the widely varying muffler designs, and the necessity of large inventories substantially increases the cost of mufflers to the ultimate consumer.

In accordance with the present invention, I provide a muffler which utilizes two shells and an insert plate which cooperates with the two shells to provide the necessary flow channels, expansion chambers and resonating chambers for filtering the objectionable noise from the exhaust gases. With the mufiler of the present invention, the three parts of relatively simple geometry replace a considerably more complex (and more expensive) mufiler designs of the past.

An object of the present invention is to provide an improved mufiler assembly consisting essentially of three basic components of relatively simple geometry.

A further object of the invention is to provide an improved mufi ler which can be manufactured at a substantially lower cost than typical muifier assemblies presently in use.

A further object of the invention is to provide a muffler assembly having a centrally disposed insert plate, and composed of material-s which are resistant to erosion by the hot exhaust gases and also by the acid combustion products which frequently appear in exhaust gases.

Broadly speaking, the mufiler assembly of the present invention includes a pair of shells, each having inwardly extending integral baflle means which form boundaries of spaced resonant chambers and expansion chambers when the shells are placed in face to face contact, together with a plate confined between the shells and including bafile means for directing gases into the expansion chambers and past spaced resonant chambers defined by the baffles on the shells and on the plate. With the muffler of the present invention, a pair of shells can be United States Patent 0 treated in FIGURES 3 and 4 of the drawings.

used as the two basic elements, and an individually designed plate whose geometry is determined by the noise characteristics of a particular engine are employed in combination to provide a very economical but highly effective noise filtering system.

Other objects and features of the present invention will be apparent to those skilled in the art from the following description of the attached sheets of drawings which describe a preferred embodiment.

In the drawings:

FIGURE 1 is a plan view of the muflier assembly, one of the shells being removed for the purpose of clarity, and the insert plate being shown in dotted outline;

FIGURE 2 is a cross-sectional view of the muffler taken substantially along line II-II of FIGURE 1, with all three components in place;

FIGURE 3 is a plan view of the other shell member; and

FIGURE 4 is a cross-sectional view taken substantially along line IV1V of FIGURE 3, with all of the components in assembled relation.

As shown in the drawings:

In FIGURE 1, reference numeral 10 indicates generally a muffler assembly produced according to the present invention. As best seen in the cross sectional view of FIGURE 2, the mufiier 10 includes three basic components, a first shell member 11, a second shell member 12, and an insert plate 13 confined between the two shell members. As seen in FIGURE 2, the first shell member 11 and the second shell member 12 have matching marginal edges 11a and 12a respectively which are arranged to abut and thereby form a gas-tight enclosure. The first shell member 11 is provided at the inlet end with a semi-cylindrical recess 14 which cooperates with a similarly formed semi-cylindrical recess 16 in the second shell member 12 to define an inlet for the exhaust gases indicated generally at numeral 17 in FIGURE 4. Similarly, at the opposite end, the first shell 11 is provided with a semi-cylindrical recess 17 which meets with a similar semi-cylindrical recess 18 in the second shell 12 to provide an exhaust chamber 19, as shown in FIG- URE 4.

The construction of the first shell member 11 is best seen in FIGURES l and 4 of the drawings. It will be seen that the first shell member 11 has a plurality of integral inwardly extending ribs 21 and 22 wich extend the .full transverse width of the shell and are spaced longiand 22 are substantially coplanar, minus the plate thickness, with the marginal edges 11a of the shell 11.

The configuration of the second shell 12 is best illus- It will be seen that the shell 12 includes a pair of bafiles 23 and 24 in confronting relationship immediately behind the gas inlet 17 in the direction of gas flow, leaving a constricted passageway 26 between the baffles 23 and 24. Within the shell 12 there is disposed a flow divider 27 having a forward wall portion 28 in line with the constriction 26 and side wall portions 22 and 31 extending in parallel relationship intermediate the center line of the shell 12 and the longitudinal marginal edges. The side wall portions 29and 31 are slightly tapered as indicated at 32 and 33 and terminate in a rear wall portion 34 near the outlet end of the muffler. Slots 36 and 37 are provided in the side wall portions 29 and 31 so that there is fluid communication between the gas paths outwardly of the side-wall portions 29 and 31 with a resonant chamber 38 defined by the interior of the flow divider 27. Near the outlet end of the mufller, the second shell 12 is provided with a transversely extending baffie 39 to channel the flow of the gases into the outlet 12, as will be explained in a succeeding portion of this description.

The shells 11 and 12 are preferably composed of a synthetic resinous material such as fiberglass or asbestos impregnated with a phenolic resin which preferably contains a carbonizing material which chars under the high temperatures prevailing to form an insulating film about the interior surfaces of the muffler. With this type of composition, temperatures of up to about 1400 F. can be tolerated in the muffler.

A configuration of the insert plate 13 is best illustrated in FIGURES 1, 2, and 4. The plate 13 includes a flat mounting portion 41 having apertures therein which fit over mounting pin 42 formed integrally with the first shell member 11. The plate 13 includes an upstanding baffle portion 43 whose height is somewhat less than the minor axis of the assembled shells in cross-section as evidenced in FIGURE 2, thereby providing a gas flow space 44- between the baffie 43 and inner wall of second shell member 12. The balfle 43 is also provided, in the form of the invention illustrated, with a pair of spaced apertures 46 and 47 which face the gas inlet 17. The gases exit through a slot 48 provided on an inclined wall portion 49 disposed immediately behind the bafile .3. Additional securing means may be provided in the form of tabs 51, 52, which are confined between the shells 11 and 12 when the shells are in assembled relation. As indicated in FIGURE 1, the plate 13 has marginal end portions 13a which are received between the marginal edge portions 11a and 12a of the shells 11 and 12 in securely clamped relation when the shells are assembled. While the manner of securing the plate between the shells shown in the drawings is presently preferred, it should be ap preciated that other types of securing means could also be employed.

Additional locating pins 53 and 54 are provided on the first shell member 11 to secure proper positioning of the plate 13 within the shells. Immediately behind the angularly disposed wall 49 is an upstanding wall portion 56 provided with an aperture 57 which the gases flow past after passing through the slot 48.

The plate 13 has a central web portion 58 which extends along the parting line between the shells 11 and 12. Intermediate the transverse baffles 21 and 22, the web portion 58 is provided with a pair of slots 59 and 61 as indicated in FIGURE 1 to form an additional resonating chamber 62 within the first shell member 11. The plate 13 is further positioned on the shell 11 by providing locating pins 63 and 64 which pass through apertures provided in tabs 66 and 67 extending from the plate 13. At the rearward end of the plate 13, there is provided a slot 68 which channels the flow of gases in the gas outlet 19 as will be apparent from the following description.

The plate 13 can be composed of any suitable material, including metals such as stainless steel. I prefer, however, to make the plate 13 of the same type of composition that constitutes the shells 11 and 12. because the fiberglass or asbestos impregnated resin is considerably cheaper, and is more resistant to acid decomposition products which appear in the exhaust gases.

In operation, the exhaust gases enter through the inlet 17 where they are immediately expanded and then confined into three flow paths consisting of the flow through the aperture 46, the aperture 47, and through the gas channel 44. The gases passing through the apertures 46 and 47 are recombined by passage through the slot 48 where they recombine with the gas from the gas channel 44. This provides, in effect, an additional expansion zone immediately behind the inclined wall portion 49 of the plate 13. The aperture 57 provides communication with a resonant chamber '71 defined by the shell 11, the plate 13, and the transversely extending bafile 21.

The flow of gases then passes through the constriction 26 whereupon it divides into two paths outwardly of the side walls 29 and 31 of the flow divider 27. In doing so, the gases pass over the slots 59 and 61 provided in the plate 13 whlch communicate with the resonant Chambgy 62. The divided gas streams also pass by the openings 36 and 37 which communicate with the resonant chamber 38 in the flow divider 27. The two flow paths are then combined beyond the wall portion 34 of the flow divider 27 and past the transverse rib 39 through the slot 68 in the plate 13. Finally, the gases enter an expansion chamber 72 defined by the shells 11 and 12 before they pass through the gas outlet 19. In the exit flow, they pass by a resonant chamber 73 defined by the first shell member 11, the plate 13, and the rear wall of the rib 22.

The specific configuration of the plate illustrated in the drawings was made for a particular model car using a particular type of engine. To accommodate different engines of similar noise characteristics, it is merely necessary to substitute for the plate 13, a different plate having the same general profile but in which the apertures are varied in spacing and geometry. For example, in a different engine, it may be advisable to replace the two apertures 16 and 47 with a single slot or to change the location of the apertures 4-6 and 4'7 along the baflle 43. Similarly, it may be advisable with another engine to change the location of the slot 68 or the'geometry of the slots 5% and 61 in the plate 13. With the mufiler assembly of the present invention, it is a simple matter to determine the proper location for these apertures by test and then provide a standard plate for use with other engines of that type.

From the foregoing, it will be seen that the mufiier assembly of the present invention provides a simplified but highly effective noise silencer for internal combustion engines. The simplicity of the three piece construction makes the mufiler assembly of the present invention very economical to manufacture.

It should be evident that various modifications can be made to the described embodiments without departing from the scope of the present invention.

1 claim as my invention:

1. A mufilcr assembly comprising a first shell and a second shell having matching marginal edges which are arranged to abut to form a gas-tight enclosure having a gas inlet and a gas outlet,

said first shell having a plurality of integral ribs extending transversely of said first shell,

said second shell havin a pair of bafiles in conrronting relationship in close proximity to said gas inlet,

said baffles having a space therebetween for permitting the passage of gas therethrough,

said second shell also having a longitudinally extending flow dividing means rearwardly of the confronting baffles in the direction of gas flow,

and a plate confined between said shells,

said plate having bafile means and apertures therein which cooperate with the ribs, baffles, and flow dividing means on said shells to define a plurality of resonant chambers and expansion chambers for gases passing between said inlet and said outlet.

2. A muffler assembly comprising a first shell and a second shell having matching marginal edges which are arranged to abut and form a gas tight enclosure having a gas inlet and a gas outlet,

said first shell having a plurality of transversely extending longitudinally spaced ribs whose inner edges are substantially coplanar with the marginal edges of said first shell,

a second shell having a pair of confronting bafi les in close proximity to said gas inlet, said confronting baifles being spaced to provide a gas passage therebetween,

said second shell also having a flow divider located rearwardly of said confronting bathe in the direction of gas flow,

said flow divider being shaped to hann l th fl of gases away from the longitudinal center and into flow paths adjoining the abuttingmarginal edges of said shells,

and a plate confined between said shells,

said plate including baffle means having apertures disposed in the region of said flow paths,

said apertures providing communications between said flow paths and the space between a pair of adjoining ribs on said first shell.

3. The mother of claim 2 in which said bafiie means on said plate is of lesser dimension than the minor axis of the assembled shells in cross-section,

thereby providing a how passage between said bathe and said shell.

4. A muffler assembly comprising a first shell and a second shell having matching marginal edges which are arranged to abut and form a gas tight enclosure having a gas inlet and a gas outlet,

said first shell having a plurality of transversely eX- tending, longitudinally spaced ribs whose inner edges are substantially coplanar with the marginal edge of said first shell,

said second shell having a constriction therein down stream from said gas inlet,

said second shell also having a How divider behind said constriction in the direction of gas flow arranged to divert the gases flowing through said constriction into two paths therearound,

said flow divider having apertures providing commu- Q nication with a resonant chamber for the gases flowing past that flow divider, said first and second shells being shaped to provide an expansion chamber behind said flow divider and ahead of said gas outlet in the direction or gas how, and a plate clamped between the first and second shells, said plate having apertures therein providing resonant chambers between said shells for gases passing through said muifier assembly. 5. The mufiler assembly of claim 4 in which said plate has a transversely extending apertured bafiie portion inlinediately behind said gas inlet,

said bafile portion extending less than the full transverse dimension of the abutting shells,

thereby providing an additional gas confining channel for gases passing through said mufller assembly.

References Cited in the file of this patent UNITED STATES PATENTS 1,758,654 Dorineyer May 13, 1930 3,031,026 Price Apr. 24-, 1962 FOREIGN PATENTS 234,854 Switzerland Feb. 16, 1945 280,315 Great Britain Nov. 17, 1927 1,018,594 France Oct. 15, 1952 

1. A MUFFLER ASSEMBLY COMPRISING A FIRST SHELL AND A SECOND SHELL HAVING MATCHING MARGINAL EDGES WHICH ARE ARRANGED TO ABUT TO FORM A GAS-TIGHT ENCLOSURE HAVING A GAS INLET AND A GAS OUTLET, SAID FIRST SHELL HAVING A PLURALITY OF INTEGRAL RIBS EXTENDING TRANSVERSELY OF SAID FIRST SHELL, SAID SECOND SHELL HAVING A PAIR OF BAFFLES IN CONFRONTING RELATIONSHIP IN CLOSE PROXIMITY TO SAID GAS INLET, SAID BAFFLES HAVING A SPACE THEREBETWEEN FOR PERMITTING THE PASSAGE OF GAS THERETHROUGH, SAID SECOND SHELL ALSO HAVING A LONGITUDINALLY EXTENDING FLOW DIVIDING MEANS REARWARDLY OF THE CONFRONTING BAFFLES IN THE DIRECTION OF GAS FLOW, AND A PLATE CONFINED BETWEEN SAID SHELLS, SAID PLATE HAVING BAFFLE MEANS AND APERTURES THEREIN WHICH COOPERATE WITH THE RIBS, BAFFLES, AND FLOW DIVIDING MEANS ON SAID SHELLS TO DEFINE A PLURALITY OF RESONANT CHAMBERS AND EXPANSION CHAMBERS FOR GASES PASSING BETWEEN SAID INLET AND SAID OUTLET. 